For example, Japanese Patent Publication 2004-220012A discloses an image formation apparatus, in which a plurality of toner bottles (developer storage members) are placed in a horizontal direction such that an opening of each toner bottles is located at a lower part of the toner bottle and directed downward (see FIG. 1 of the publication). Because the opening of each toner bottle is located at the lower part and directed downward, the developer stored in the toner bottle can be supplied well from the opening.
In case where an image formation apparatus is designed such that developer storage members are juxtaposed in a substantially vertical direction and an opening of each developer storage member is located at a lower part thereof and directed downward, the developer storage members need to be spaced away from each other in the vertical (up and down) direction. Otherwise, a conveying passage for conveying a developer from the opening of an upper developer storage member interferes with an adjacent lower developer storage member. On the other hand, if the developer storage members are spaced away from each other in the up and down direction, the image formation apparatus becomes larger in size in the up and down direction and a space above the image formation apparatus can not be used effectively.